in-line heater?

I was wondering if in-line heaters are more efficient than normal heaters even if the normal heater is placed in a location of high flow? any one have any experience with in-line heaters?

 

I haven't had experience with them. But, I would think they would be more efficient because the heat is being distributed much more faster, that just a heater smacked on the glass

 

i thought the samething. However IMO they are meant for canister filters. Sticking a heater in a sump works just as well i find.

 

I used to want to purchase one until I did more research. In order to not be on all the time, you need slow flow through it. The heating elements are just like the ones on the back window of a car. A normal heater is more efficient and easier to use.

 

I think it would be important (just like anything) to size it right so you have the right flow through it. Part of me thinks it would be better and part thinks that if you have good flow on your heater in the sump it would be just as good.

 

Efficiency is a matter of energy in energy out. An electric immersion heater is 100% efficient. That is to say 100% of the electricity used in the heater is converted to heat in the water. ANY electric immersion heater will be the same.

There was some folks wanting to use some heater pads placed under the tank. The heat would need to be insulated from the outside world to prevent heat escape. The heat that did go into the tank would have to pass through the sand layer and glass to get to the water. In that case you would come up with a number of "X" amount of electrical watts endded up as degrees F in the tank. It would be hard to come up with 100%.

You would have no advantage using one over the other in your case. Both have adequate flow to transfer heat to the water. As far as time that is simply a function of heat transfer rate. The higher the wattage the faster the transfer given equal water flow rates. Heating "faster" is not really a function of efficiency. Hope that helps.

 

I thought that in-line heaters had more surface area for the heating element and got more heat exchange with the same or lower watts.

 

If a heater is rated at 400watts... then that is actually 400 per hour of power. That 400w per hour will be converted to 1365 BTUs per hour. So watts is a direct convert to heat content over a given time. So if you had a 300w standard heater and a 300w in-line... then over an hour they are still going to put out the same heat.

Surface area most definitely matters to heat transfer, but so do other factors as well. So for our heaters that sit in direct contact with the cooling fluid, surface area is not the limiting factor. Temp difference and fluid flow are more than enough to get that 300w of power out of either heater. Does that make sense?

The in-line may very well be capable of transfering its heat faster, but it will only transfer what it is rated for. Nothing is free. You don't get more heat for less watts.

 

the way I see it is that if you have the heat transferring faster with the same watts in the end on the same amount on time/power usage you will have transferred more heat for the same amount of power. If I have a heater of x watts that transfers heat faster than a heater of equal watts it will take less time to bring my water to temp and my heater will go off quicker saving me power/$ in the long run. I agree that nothing is free and your not going to get heat for nothing, but the idea is that your having a heat buffer develop in the water creating a slight reduction of temp exchange. I think yellow tang had it right that most of us have our heaters on the glass or off to the side in the sump and that would not have nearly as good of heat transfer as a in-line because one side would not have proper flow.

 

But power use is direct heat use. 300w heater can only put out 300w per hour. The fact that a cooling media removes that heat faster does not allow the heater to put out 350w in a hour. Watts are BTUs... you can only put out so many.

Say we have a 100 lbs of water at 78F and we want to raise it to 80F... we need 200 BTUs. A 300w heater would roughly need 10 minutes to do that in. No if we had a heater that needed 15 minutes to do the same job, then so be it. But it still puts out 200 btus and still shuts off. It's heat transfer rate may be slower, but we are not maxed out for time.

If you had a heater in a slow flow area that used it's own thermostat...the water would heat up locally and the heater would turn off before warming up the rest of the tank. That would be a flow problem, not a heat transfer problem. If you submerge two electric heater rated at the same out put and then gave them equal cooling (water flow) then results will still be only 300 watts of heat per hour.

Right, and that is a flow problem, not a heater efficiency problem. Reduce the flow on the inline to the same and you will get the same results.

You are not out in left field.... the rate at which a heater can transfer heat is definitely important... but only if it is the limiting factor.... which it isn't.

Let's say this... we only have a 100w heater yet our tank losses 150w of heat per hour. Both heater would be on 100% of the time and neither would heat the tank effectively. We may then find that the in-line can keep the tank just a bit warmer just because it is making the most out of the flow it has.

But then we put on a 300w heater and both only run 50% of the time. that 300w is a max but that does not mean it runs max on and off. So an inline may only run 27 minutes and the other run 33 minutes.... but you are not using 300w exactly in both.... you are only using the amount of heat(watts) you need to get the tank up to set point.

Most sumps have enough flow to get the job done. One reason I sugest to others to put the heater in the return section is to ensure good flow. So as long as flow is equal, a in line is not better.

And again.... at least efficiency is only based on total energy input and total energy out put.... so a immersion heater such as a tube or a in-line is 100% (99%?) efficient at doing it's job. That job is to convert electrical energy input into heat out put. A heater hung above the sump would still be 100% efficient at converting electricity into heat.... but it would suck at heating the tank. It's heat transfer rate to the sump would be nearly non existent.